Gasproofing leaking gas main



W. E. KEMP April 18, 1%?

GASPROOFING LEAKING GAS MAIN Filed Dec. 13, 1965 I NVENTOR.

KE'MP The weight ratio of the tar-rubber 3,3 15,0l 7 Patented Apr. 18,1967 3,315,017 GASPROOFHNG LEAKING GAd MAIN Woodrow E. Kemp, Pittsburgh,Pa., assignor to Koppel-s ompauy, Inc., a corporation of Delaware 7Filed Dec. 13, 1963, Ser. No. 330,464

10 Claims. (Cl. 264-36) been further aggravated by the necessity ofincreasing line pressures in order to meet increased demands.

One solution to the problem is to excavate at the end pair over extendedperiods of time. 7

It is, therefore, an object of the present invention to provide asimplified way of sealing bell and spigot joints of cast iron pipeswhich eliminates the to seal each lasting sealing composition which canbe readily applied from inside the pipes.

In accordance with the present invention, I have discovered that belland spigot joints of cast iron pipes be sealed internally by contactingsaid joints from the interior surface with a sealing composition at atemperature of ZOO-450 F. and a pressure of 50-200 p.s.1.g. Thecomposition comprises a three to "seven percent of a copolymer of 45-20parts by weight of acrylonitrileand 55-80 parts by weight of butadienein coal tar pitch together with an inert filler. solution to the filleris and the composition has F. within the range of 1000- within the rangeof 19:1 to 3:1 a Brookfield viscosity at 250 14,000 centipoises.

The environment in which the sealing compound is to be used is primarilynatural gas with occasional exposure topropane air mixtures or gasproduced by thermal cracking of petroleum oil which may contain aromaticoils and heavy unsaturated and aromatic hydrocarbons. In order to beeconomically feasible, the seal produced between abutting sections ofpipe should last for an extended period of at least about years.

The rubber in the tar-rubber solution is a copolymer of acrylonitrileand butadiene, which is comprised of a major portion, 55-80 parts byweight of -butadiene-1,3, and a minor portion, correspondingly 45-20parts by weight of acrylonitrile. It is a commercially availablematerial having a government synthetic rubber designation of GR-A. Thehigher the acrylonitrile content the harder it is to dissolve thecopolymer in the tar; the lower the acrylonitrile content, the lessresistance the film has to solvents, such as paraflinic or naphthenicoils.

To facilitate the solution in the coal tar and reduce the mixer scheduletime, the copolymer may be broken down on a rubber mill. A convenientcopolymer for use in this invention is a butadiene-acrylonitrilesynthetic rubber sold under the trademark Hycar and having a Mooneyviscosity of from -100. The Hycar Type 1442 is sold in crumb form andreadily goes into solution. The copolymer additionally gives the filmelasticity, ductility, and reduced susceptibility to temperaturechanges. It has been found that if the amount of copolymer be less thanthree per cent by weight of The coal tar pitch in which the copolymer isdissolved may be of the types conventionally designated as RT-6 to RT-12which are defined in ASTM Standards D490-47. Such tars have an overallfloat test, commonly used for testing the viscosity of semi-solidbituminous material, ranging from 20 seconds to 220 seconds asdetermined by ASTM Test Dl39-49.

The copolymer is readily dissolved in the tar by maintaining the tarunder agitation at an elevated temperature while the copolymer is addedto the tar. The copolymer does not dissolve well if the temperature ofthe tar is below 230 F., but if the temperature be greater than 315 F.the breakdown temperature of the copolymer is and the copolymer beginsto decompose. The

tar Without separation or sludging.

The filler serves primarily as a viscosity increasing ingredient.Suitable inert fillers useful in my invention include sand, asbestosfibers, fiberglass, talc, and the like which may be used alone or inmixtures thereof. These are generally used in an amount ranging fromabout 5-25 percent of the total weight which corresponds to a weightratio of tar-rubber solution to filler within the range of 19:1 to 3:1.When less than five percent is used, the sealing composition tends toflow out of the joints, whereas perature of around 250 F. Alternatively,the fillermay be mixed with the copolymer and the mixture added withagitation to the heated tar.

The above and in connection with the accompanying drawings. It is to beexpressly understood, however, that the drawings are not intended as adefinition of the invention, but are for the purposes of illustrationonly.

In the drawings wherein like parts are marked alike:

FIGURE 2 is an elevational view with portions broken out of anotherembodiment of the novel apparatus.

Referring to the drawing, FIGURE 1, it is conventional for sections ofcast iron pipe 11 to be joined by a bell and spigot joint E2. The bellis a flared portion and the spigot is a beaded portion such that in thepipe line the spigot end slopes into the bell end forming a. spacetherebetween.

Conventionally, the cast iron pipe for such environments has a sizebetween 4-48 inches and primarily in the range of 4-12 inches with thespace between abutting sections of pipe being up to one-half inch wideand approximately one inch deep. This piping is subject to some movementas a result of settling and traffic vibrations and as a result of thelinear expansion of the cast iron. Typically, the pressure in the sixinch section of pipe is from 2-60 p.s.i.g. and the ground temperature isbetween 30-90 F.

The vibration and expansion of the sults after a period of time inleakage. To repair the seal so as to eliminate this leakage has been adifficult and expensive operation. It has involved, for example, diggingholes every few feet and mechanically sealing the bell and spigot jointsparticularly from the outside joint.

In accordance with this invention there is provided a novel and simplemanner of sealing the joints by forcing a sealing composition into thespace between the joints internally of the pipe, thereby eliminating theneed for uncovering the external surface of the pipe so as to seal thejoint. In addition, the invention has the advantage that the seal isinternal and therefore in the direction of the tendency to leak therebyblocking leakage which would be difiicult to ascertain by visualinspection.

The sealing of the pipe internally is accomplished by a novel apparatuscomprising generally a pair of circular cast iron pipe re- -discs and 17separated by spacer member 19 and in- 21 for the sealing compositionalong with a heating unit 23 for maintaining the sealing composition 25at an operative viscosity.

Discs 15 and 17 may be substantially identical. In each disc asillustrated herein, the disc comprises a front portion 15f of rigidmaterial such as metal, a gasket 16 able to withstand internal pressureduring operation, and a rear portion 151' of rigid material such asmetal. The gasket is thus sandwiched between the front and rear portionsand provides a seal so that the assembly has a circumferencesubstantially equal to the inside circumference of the pipe thusmaintaining intimate contact therewith. Since these two discs 15 and =17are held in spaced apart arrangement, a chamber 14 is formed togetherwith the inside walls of the pipe 11 for the sealing composition 25.

As illustrated herein, the spacers 19 are fastened to discs 15 and 17 soas to maintain the discs parallel to each other and normal to the axisof the pipe. The spacers 19 are advantageously a plurality of rodsalthough other shapes of spacers may obviously be used.

Disc 17 has an aperture therein in which is held the member forintroducing the composition under pressure into chamber 14. Asillustrated herein a flexible hose 21 is secured for example by a locknut 22 to disc 17. Thus the composition can be introduced into chamber14 by a suitable source not shown such as a pump and reservoir of thecomposition.

The composition tends to become less viscous as the temperatureincreases. Accordingly, the flexible hose 21 is advantageously providedwith a means for maintaining the composition flowing through at apredetermined temperature. To this end, a heating element 23, which maybe a metallic resistor, is passed through the flexible hose 21 andaround a spacer 19.

As an illustration of the invention, a suitable tank steam jacketed ischarged with the desired quantity of coal tar pitch, RTl2, having aviscosity of 220 seconds float at 50 C. as determined by ASTM TestDl39-49. After bringing the temperature of the tar to approximately 300F. the acrylonitrile-butadiene copolymer known as Hycar 1442 is chargedthrough a chopper while maintaining good agitation with a suitableagitator, e..g., a turbine type. Agitation is continued with frequentsampling for consistency until the rubber is entirely dissolved. Thistakes approximately 1216 hours. Thereafter, the temperature is allowedto drop to approximately eluding a flexible inlet 250 F. and thefillers, e.g., asbestos fibers and talc, are charged slowly whilemaintaining agitation. The amount of filler added and the type of fillerdepends on the end viscosity and the flow characteristics desired forthe partioular service.

Typically 72.9 parts by Weight of the coal tar pitch is charged,followed by 4.6 parts of the copolymer rubber which is dissolved to forma rubber-tar solution. There is then charged approximately ten parts byweight of magnesium silicate, 325 mesh, and short fibered asbestos knownas 7M grade l2.5 parts to make a total of parts. After all theingredients are thoroughly dispersed, the mixture is charged intosuitable drums or containers which preferably have been lined with asilicon oil or silicon tight release paper to prevent sticking to themetal container and permits easy removal of the solid sealant.

In the field, the composition is charged into a kettle and heated to atemperature of approximately 250- 300 F. The material which had beensolid becomes a liquid at this temperature. The kettle is preferablyplaced near the excavation that is made to uncover a suitable bell holein the transmission gas main. After opening the gas main, a heatedmetallic flexible hose is connected to the kettle containing the moltensealant. This short length of hose in turn is connected to a suitablepneumatic pump. From the pump the flexible hose leads to a travelingplug device, of the type shown in the attached drawings, and this inturn is pulled through the pipe from another bell hole which may be 500-1000 feet distance. The pressurizing pump is started and the travelingpullplug pulled through the pipe until an electromagnetic I locaterlocates a joint. The pressure is raised to approximately 100 p.s.i.g.The traveling plug kept at that spot for about 60 seconds givingadequate time for the seal ant to flow into the joints and seal thepipes. The pressure is then reduced and the plug hauled along the pipe.If a side tap is located by the electromagnetic locater the pressure isdropped completely and the plug rapidly pulled past the opening so thatno sealant will enter the service lines. When the next joint is located,the plug is again stopped, the pressure built up, and the sealant forcedinto the joint as previously described.

The sealed joint is characterized by the following combination ofproperties:

(1) Impermeability to natural gas, propane-air mixtures and gas producedby thermal cracking of petroleum oil;

(2) A high degree of elasticity, especially in the required temperaturerange of 3090 F., to be able to withstand pipe movement as a result ofsettling, traflic vibrations, and expansion of the cast iron pipewithout the sealant becoming brittle;

(3) Formation of an adhesive bond between the sealant and uncleaned castiron pipe;

(4) A high solvent resistancy, and naphthenic oils;

(5) Flow properties of the sealant being such that the sealant will notflow from the sealed joint;

(6) The joints are pressure sealed with the sealant composition in thesame direction as the gas tends to flow therefrom; and

(7) A long service life of at least about 15 years to make the sealingprocess economically feasible.

FIGURE 2 illustrates another embodimentof the novel apparatus forcarrying out the invention. In this embodiment the structure isgenerally similar to the structure of FIGURE 1, that is, having discs 15and 17 and a flexible hose 21. However, in this embodiment spacer 19 isfixed to disc 17 but by a suitable seal spacer 19 is movable relative todisc 15. In addition, through disc 17 extends suitably pressure sealed ashaft 31 of a conventional motor 33 which is secured by conventionalmeans such as, for example, attached to bracket 35. The shaft of thismotor terminates as a thread or worm 37. This worm especially toparafiinic ttowardseach other the pressure then threads into nut 39suitably fixed to disc 15. Thus as the motor turns, shaft 31 threadsinto 'nut 39 thereby moving disc relative to disc 17.

In accordance with this'invention, the novel composition is flowed intocha-mber 14, thereafter motor 33 is actuated causing thread 37 to turnthereby causing relative movement of discs 15 and 17. Thus, as the discsmove on the composition 25 in chamber 14 becomes greater than thepressure in flexible hose 21 causing the sealant composition, which hasnot flowed into the bell and spigot joint, to flow back into thereservoir. As the discs 15 and 17 contact each other, the chamber hasdecreased or disappeared so that the apparatus may be moved through thepipe without danger of composition flowing into branch lines.

The foregoing has described a novel manner for sealing the joints ofcast iron pipe without the heretofore trouble of digging the pipe todetermine where the joints are and visually inspecting the joint todetermine the leakage. The composition is permanent, is flexible, and isadhesive and the omt 1n the same tra distinction to the usual type ofrepair of the joint where the joint is repaired from the outside and thepressure building up within the pipe tends to force away the externalseal.

I claim:

1. A method for internally sealing the joint between lengths of pipecomprising the steps:

(a) moving a traveling plug through said pipes to the vicinity of saidjoint, said plug being adapted to straddle said joint and seal otf anenvironment, within said pipes and on both sides of said joint, from theremainder of said pipes;

(b) flowing into said environment under pressure a sealant comprising atar-rubber solution containing acrylonitrile and butadiene in coal tarpitch together with an inert filler at a temperature of 200-450 F.;

(c) maintaining said sealant under a pressure in the range of 50-200p.s.i.g. for a period of time long enough for said sealant to penetrateand seal said joint;

(d) reducing said pressure in said environment to ambient within saidpipe; and

(e) moving said traveling plug away from said joint along said pipes.

2. The method of claim 1 including the step:

(a) maintaining the temperature of the sealant in said environment at atemperature in the range of 200- 450 F. t

3. A method for sealing the joint between lengths of pc from the insideof said pipes comprising the steps:

(a) moving a traveling plug through said pipes to the vicinity of saidjoint, said plug being adapted to straddle said joint and seal off anenvironment, within said pipes and on both sides of said joint, from theremainder of said pipes;

(b) flowing into said environment under a pressure in the range of50-200 p.s.i.g. a sealing composition at a temperature in the range ofZOO-450 F. comprising 3 to 7 percent filler, the weight ratio of saidtar-rubber solution to said filler being within the range of 19:1 to3:1;

(c) maintaining said sealant under a pressure in the range of 50-200p.s.i.g. for a period of time long enough for said sealant to penetrateand seal said joint;

(d) reducing said pressure in said environment to ambient within saidpipe; and

(e) moving said traveling plug along said pipe away from said joint.

4. A method for internally sealing the joint between lengths of pipeadapted for carrying a fluid comprising the steps:

(a) moving a traveling plug through said pipes to the vicinity of saidjoint, said plug being adapted to straddle said joint and seal oif anenvironment, within said pipe and on both sides of said joint, from theremainder of said pipes;

(b) flowing into said environment under a pressure in the range of50-200 p.s.i.g. a sealing composition comprising a tar-rubber solutioncontaining from 3 to 7 percent of a copolymer of to 20 parts by weightof acrylonitrile and 55 to 80 parts by weight of butadiene in coal tarpitch and an inert filler, the weight ratio of said tar-rubber solutionto said filler being within the range of 19:1 to 3:1, said compositionhaving a Brookfield viscosity at 250 F. in the range of 1,000-14,000centipoises whereby said joint is pressure sealed, said compositionflowing into said joint in the same direction as the fluid flow in saidp (c) maintaining said sealant under a pressure in the range of -200p.s.i.g. for a period of time long enough for said sealant to penetrateand seal said joint;

(d) reducing said pressure in said environment to ambient within saidpipe; and

(e) moving said traveling plug along said pipes away from said joint.

5. The method according to claim 4 wherein:

(a) said filler is selected from the group consisting of sand, asbestosfibers, glass fibers, talc, and mixtures thereof.

6. A method for internally sealing a leaking joint be tween lengths ofpipe comprising the steps:

(a) locating leaking joint between adjacent lengths of (b) moving atraveling plug through said pipes to the vicinity of said leaking joint,said plug being adapted to straddle said leaking joint and seal ofl anenvironmerit within said pipe on both sides of said joint from theremainder of said pipes;

(c) flowing into said environment a sealing composi tion heated to atemperature in the range of 200- 450 F. and comprising a tar-rubbersolution containing acrylonitrile and butadiene in coal tar pitchtogether with an inert filler; and

(d) moving one portion of said plug relative to the remainder of saidplug within said pipes so as to exert a pressure on said sealingcomposition greater than the external pressure around said leaking jointwhereby said sealing composition flows into said leaking joint and sealsthe same.

7. The method according to claim 6 wherein:

(a) said sealing composition comprises a tar-rubber solution containingfrom 3-7 percent of a copolymer of 49-20 parts by weight range of 19:1to 3:1.

8. The method according to claim 6 wherein:

composition comprises a tar-rubber 7 percent of a coto 20 parts byweight of acrylonitrile and to parts by weight of butadiene in coal tarpitch and an inert filler, the. weight ratio of said tarrubber solutionof said filler being within the range of 19:1 to 3:1; and

(b) said composition has a Brookfield viscosity at 250 F. Within a rangeof 1000-14,000 centipoises.

9. The method according to claim 8 including the step:

(a) maintaining the temperature of said sealing composition within saidenvironment in the range of ZOO-450 F.

7 8 10. The method according to claim 9 wherein: 3,172,934 3/1965 Krieg264-263 (a) said filler is a substance selected from the group 3,182,1104/1965 Balcom et a1. 264-263 consisting of sand, asbestos fibers, glassfibers, talc 3,267,967 8/1966 Guthrie 138-97 and mixtures thereof. 5FOREIGN PATENTS References Cited by the Examiner 547,821 1942 GreatBritain.

UNITED STATES PATENTS OTHER REFERENCES 393,381 11/ 1888 McSWeeney 64- 6Acrylonitrile, Union Carbide Chemicals Company 694,196 2/1902 Rose 25-38X Technical Publication, p. 5 (1960). 907,724 12/1908 Boyle 25-38 101,736,293 11/ 1929 Van Denberg 264-36 X ROBERT F. WHITE, PrimaryExaminer. 1,946,619 2/1934 Furman et a1 X L. s. SQUIRE'S, T. J. CARVIS,Assistant Examiners.

3,168,909 2/1965 Zurbrigen et a1. 138-97

6. A METHOD FOR INTERNALLY SEALING A LEAKING JOINT BETWEEN LENGTHS OFPIPE COMPRISING THE STEPS: (A) LOCATING LEAKING JOINT BETWEEN ADJACENTLENGTHS OF PIPE; (B) MOVING A TRAVELING PLUG THROUGH SAID PIPES TO THEVICINITY OF SAID LEAKING JOINT, SAID PLUG BEING ADAPTED TO STRADDLE SAIDLEAKING JOINT AND SEAL OFF AN ENVIRONMENT WITHIN SAID PIPE ON BOTH SIDESOF SAID JOINT FROM THE REMAINDER OF SAID PIPES; (C) FLOWING INTO SAIDENVIRONMENT A SEALING COMPOSITION HEATED TO A TEMPERATURE IN THE RANGEOF 200450*F. AND COMPRISING A TAR-RUBBER SOLUTION CONTAININGACRYLONITRILE AND BUTADIENE IN COAL TAR PITCH TOGETHER WITH AN INERTFILLER; AND (D) MOVING ONE PORTION OF SAID PLUG RELATIVE TO THEREMAINDER OF SAID PLUG WITHIN SAID PIPES SO AS TO EXERT A PRESSURE ONSAID SEALING COMPOSITION GREATER THAN THE EXTERNAL PRESSURE AROUND SAIDLEAKING JOINT WHEREBY SAID SEALING COMPOSITION FLOWS INTO SAID LEAKINGJOINT AND SEALS THE SAME.